This invention relates to an impression cylinder device of a sheet-fed printing press with a turn-over mechanism in which the trailing end of a sheet of paper to be turned over is wound about the surface of the impression cylinder for sucking while maintaining the trailing end spaced from the impression cylinder surface.
Sheet-fed printing presses provided with various types of turn-over mechanism have been proposed for performing single side printing and double side printing with the same printing press. According to one type, a sheet of paper is sucked and turned over between an impression cylinder and a turn-over cylinder for performing the double side printing.
The printing press of this type comprises a blanket cylinder, an impression cylinder urged against the blanket cylinder and having a double diameter, and a turn-over cylinder urged against the impression cylinder and having a double diameter. When performing the double side printing with this printing press, after printing, the sheet of paper is gripped by the grippers of the impression cylinder and wrapped about the periphery of the impression cylinder until the trailing end of the sheet comes to confront the turn-over cylinder. Then the trailing end of the sheet is sucked by the suction device of the turn-over cylinder to be gripped by the turn-over gripper. The sheet of paper is conveyed while being turned over by the rotation of the turn-over cylinder. Thus, the turned-over paper sheet is transferred to the next printing cylinder to be printed on the rear surface, thus performing the double side printing.
However, the sheet of paper thus turned-over for performing the double side printing adheres to the periphery of the impression cylinder because the space between the sheet of paper and the impression cylinder is evacuated due to the pressure applied between the blanket cylinder and the impression cylinder during printing. Accordingly, it is difficult to peel off the sheet of paper away from the peripheral surface of the impression cylinder by the suction device for the purpose of turning-over the paper sheet. Accordingly the turn-over grippers offen fail to grip the sheet of paper.